Most of the radio spectrum in the United States has already been allocated for use by some type of wireless device. This leaves very little unallocated spectrum available for new wireless devices. It is predicted that with the rapid growth of global mobile network data traffic, we will face increasingly severe bandwidth shortage (i.e., a bandwidth crunch). However, while most of the radio spectrum has already been allocated, measurements have shown that most of the allocated spectrum is only lightly utilized at any given point in time. The obvious inefficient use of the radio spectrum has motivated a closer look at the current spectrum regulatory policies and spurred the advent of technologies such as dynamic spectrum management (DSM) and cognitive radios, which may offer solutions to the bandwidth crunch problem.